﻿/*
	© 2015-2023 FrankHB.

	This file is part of the YSLib project, and may only be used,
	modified, and distributed under the terms of the YSLib project
	license, LICENSE.TXT.  By continuing to use, modify, or distribute
	this file you indicate that you have read the license and
	understand and accept it fully.
*/

/*!	\file string_view.hpp
\ingroup YStandardEx
\brief 只读字符串视图。
\version r663
\author FrankHB <frankhb1989@gmail.com>
\since build 640
\par 创建时间:
	2015-09-28 12:04:58 +0800
\par 修改时间:
	2023-02-07 00:57 +0800
\par 文本编码:
	UTF-8
\par 模块名称:
	YStandardEx::StringView
\see ISO C++17 [string.view] 。
\see WG21 N4480 7[string_view] 。

提供 ISO C++17 标准库头 <string_view> 兼容的替代接口和实现。
除了部分关系操作使用 operators 实现而不保留命名空间内的声明及散列支持提供偏特化外，
其它接口同 std::string_view 。
原始设计主要来自 Library fundamental TS ，参见 WG21 P0220R1 。
注意因为一些兼容问题， std::experimental::string_view 不被可选地使用，
	以便支持和 std::string 的交互性。
*/


#ifndef YB_INC_ystdex_string_view_hpp_
#define YB_INC_ystdex_string_view_hpp_ 1

#include "range.hpp" // for "range.hpp", ystdex::reverse_iterator;
// NOTE: See "placement.hpp" for comments on inclusion conditions.
#include "hash.hpp" // for internal "hash.hpp", is_fast_hash;
#if (YB_IMPL_MSCPP >= 1910 && _MSVC_LANG >= 201603L) \
	|| (__cplusplus >= 201703L && __has_include(<string_view>))
#	include <string_view>
// NOTE: Since WG21 P0941R2, the macro value is combined as '201606L' with WG21
//	P0254R2 support which is not used here, so the check remains the value in
//	WG21 P0941R1.
#	if (YB_IMPL_MSCPP >= 1910 && _MSVC_LANG >= 201603L) \
	|| __cpp_lib_string_view >= 201603L
#		define YB_Has_string_view 1
#	endif
#endif
#if YB_Has_string_view == 1
#	include <libdefect/string.h>
#else
#	include "cstring.h" // for std::char_traits, std::allocator, 'str_find*',
//	'str_rfind*', std::basic_ostream, std::basic_string;
#	include "operators.hpp" // for totally_ordered;
#	include <limits> // for std::numeric_limits;
#	include <stdexcept> // for std::out_of_range;
#	include "hash.hpp" // for std::hash, ystdex::hash_range;
#endif

/*!
\brief \c \<string> 特性测试宏。
\see ISO C++20 [version.syn] 。
\see WG21 P0254R2 。
\see WG21 P0941R2 2.2 。
\see https://docs.microsoft.com/cpp/visual-cpp-language-conformance 。
\see https://docs.microsoft.com/cpp/preprocessor/predefined-macros 。
\since build 837
*/
//!@{
#ifndef __cpp_lib_string_view
#	if (YB_IMPL_MSCPP >= 1910 && _MSVC_LANG >= 201606L) \
	|| __cplusplus >= 201606L
#		define __cpp_lib_string_view 201606L
#	endif
#endif
//!@}

namespace ystdex
{

//! \since build 833
inline namespace cpp2017
{

#if YB_Has_string_view == 1
//! \since build 833
using std::basic_string_view;
#else
//! \since build 640
//!@{
//! \ingroup YBase_replacement_features
template<typename _tChar, class _tTraits = std::char_traits<_tChar>>
class basic_string_view
	: yimpl(private totally_ordered<basic_string_view<_tChar, _tTraits>>)
{
public:
	using traits_type = _tTraits;
	using value_type = _tChar;
	using pointer = _tChar*;
	using const_pointer = const _tChar*;
	using reference = _tChar&;
	using const_reference = const _tChar&;
	using const_iterator = yimpl(const _tChar*);
	using iterator = const_iterator;
	using const_reverse_iterator = ystdex::reverse_iterator<const_iterator>;
	using reverse_iterator = const_reverse_iterator;
	using size_type = size_t;
	using difference_type = ptrdiff_t;
	static yconstexpr size_type npos = size_type(-1);

private:
	const_pointer data_;
	size_type size_;

public:
	yconstfn
	basic_string_view() ynothrow
		: data_(), size_()
	{}
	YB_NONNULL(2) yconstfn
	basic_string_view(const _tChar* str)
		: data_(str), size_(traits_type::length(str))
	{}
	//! \since build 861
	YB_NONNULL(2) yconstfn
	basic_string_view(const _tChar* str, size_type len) ynothrowv
		: data_(str), size_(len)
	{}
	yconstfn
	basic_string_view(const basic_string_view&) ynothrow = default;

	yconstfn_relaxed basic_string_view&
	operator=(const basic_string_view&) ynothrow = default;

	YB_ATTR_nodiscard YB_PURE yconstfn const_iterator
	begin() const ynothrow
	{
		return data_;
	}

	YB_ATTR_nodiscard YB_PURE yconstfn const_iterator
	end() const ynothrow
	{
		return data_ + size_;
	}

	YB_ATTR_nodiscard YB_PURE yconstfn const_iterator
	cbegin() const ynothrow
	{
		return data_;
	}

	YB_ATTR_nodiscard YB_PURE yconstfn const_iterator
	cend() const ynothrow
	{
		return data_ + size_;
	}

	YB_ATTR_nodiscard YB_PURE yconstfn const_reverse_iterator
	rbegin() const ynothrow
	{
		return const_reverse_iterator(end());
	}

	YB_ATTR_nodiscard YB_PURE yconstfn const_reverse_iterator
	rend() const ynothrow
	{
		return const_reverse_iterator(begin());
	}

	YB_ATTR_nodiscard YB_PURE yconstfn const_reverse_iterator
	crbegin() const ynothrow
	{
		return const_reverse_iterator(cend());
	}

	YB_ATTR_nodiscard YB_PURE yconstfn const_reverse_iterator
	crend() const ynothrow
	{
		return const_reverse_iterator(cbegin());
	}

	YB_ATTR_nodiscard YB_PURE yconstfn size_type
	size() const ynothrow
	{
		return size_;
	}

	YB_ATTR_nodiscard YB_PURE yconstfn size_type
	length() const ynothrow
	{
		return size_;
	}

	YB_ATTR_nodiscard YB_PURE yconstfn size_type
	max_size() const ynothrow
	{
		// NOTE: This is same to libc++ but not libstdc++.
		return std::numeric_limits<size_type>::max();
	}

	YB_ATTR_nodiscard YB_PURE yconstfn bool
	empty() const ynothrow
	{
		return size_ == 0;
	}

	YB_ATTR_nodiscard YB_PURE yconstfn const_reference
	operator[](size_type pos) const
	{
		return yconstraint(pos < size_), data_[pos];
	}

	yconstfn const_reference
	at(size_type pos) const
	{
		return pos < size_ ? data_[pos]
			: (throw std::out_of_range("string_view::at"), data_[0]);
	}

	YB_ATTR_nodiscard YB_PURE yconstfn const_reference
	front() const
	{
		return yconstraint(0 < size_), data_[0];
	}

	YB_ATTR_nodiscard YB_PURE yconstfn const_reference
	back() const
	{
		return yconstraint(0 < size_), data_[size_ - 1];
	}

	YB_ATTR_nodiscard YB_PURE yconstfn const_pointer
	data() const ynothrow
	{
		return data_;
	}

	yconstfn_relaxed void
	remove_prefix(size_type n) ynothrowv
	{
		yconstraint(n <= size_), yunseq(data_ += n, size_ -= n);
	}

	yconstfn_relaxed void
	remove_suffix(size_type n) ynothrowv
	{
		yconstraint(n <= size_), size_ -= n;
	}

	yconstfn_relaxed void
	swap(basic_string_view& s) ynothrow
	{
		std::swap(data_, s.data_),
		std::swap(size_, s.size_);
	}

	YB_NONNULL(2) size_type
	copy(_tChar* s, size_type n, size_type pos = 0) const
	{
		yconstraint(s);
		if(pos <= size_)
		{
			const auto rlen(std::min<size_type>(n, size_ - pos));

			std::copy_n(data_ + pos, rlen, s);
			return rlen;
		}
		throw std::out_of_range("string_view::copy");
	}

	YB_ATTR_nodiscard yconstfn basic_string_view
	substr(size_type pos = 0, size_type n = npos) const
	{
		return pos <= size_ ? basic_string_view(data_ + pos,
			std::min(n, size_type(size_ - pos)))
			: throw std::out_of_range("string_view::substr");
	}

	YB_ATTR_nodiscard yconstfn int
	compare(basic_string_view s) const ynothrow
	{
		return compare_remained(s, _tTraits::compare(data(), s.data(),
			std::min<size_type>(size(), s.size())));
	}
	YB_ATTR_nodiscard yconstfn int
	compare(size_type pos1, size_type n1, basic_string_view s) const
	{
		return substr(pos1, n1).compare(s);
	}
	YB_ATTR_nodiscard yconstfn int
	compare(size_type pos1, size_type n1, basic_string_view s, size_type pos2,
		size_type n2) const
	{
		return substr(pos1, n1).compare(s.substr(pos2, n2));
	}
	YB_ATTR_nodiscard YB_NONNULL(2) yconstfn int
	compare(const _tChar* s) const
	{
		return compare(basic_string_view(s));
	}
	YB_ATTR_nodiscard YB_NONNULL(4) yconstfn int
	compare(size_type pos1, size_type n1, const _tChar* s) const
	{
		return substr(pos1, n1).compare(basic_string_view(s));
	}
	YB_ATTR_nodiscard YB_NONNULL(4) yconstfn int
	compare(size_type pos1, size_type n1, const _tChar* s, size_type n2) const
	{
		return substr(pos1, n1).compare(basic_string_view(s, n2));
	}

private:
	YB_ATTR_nodiscard yconstfn int
	compare_remained(basic_string_view s, int ret) const ynothrow
	{
		return ret == 0 ? (size() == s.size() ? 0
			: (size() < s.size() ? -1 : 1)) : ret;
	}

public:
#define YB_Impl_StringView_search_fn_head(_n, _attr, _spec, ...) \
	YB_ATTR_nodiscard YB_PURE yconstfn_relaxed _attr size_type \
	_n(__VA_ARGS__) const _spec \
	{
#define YB_Impl_StringView_search1(_n, _arg) \
	YB_Impl_StringView_search_fn_head(_n, , ynothrow, basic_string_view s, \
		size_type pos = _arg) \
		return ystdex::str_##_n<value_type, size_type, traits_type, \
			npos>(data_, size_, s.data_, pos, s.size_); \
	}
#define YB_Impl_StringView_search34(_n, _arg) \
	YB_Impl_StringView_search_fn_head(_n, YB_NONNULL(2), , const _tChar* s, \
		size_type pos, size_type n) \
		return yconstraint(s), _n(basic_string_view(s, n), pos); \
	} \
	YB_Impl_StringView_search_fn_head(_n, YB_NONNULL(2), , const _tChar* s, \
		size_type pos = _arg) \
		return _n(s, pos, traits_type::length(s)); \
	}
#define YB_Impl_StringView_search_mf(_n, _arg) \
	YB_Impl_StringView_search1(_n, _arg) \
	YB_Impl_StringView_search_fn_head(_n, , ynothrow, _tChar c, \
		size_type pos = _arg) \
		return ystdex::str_##_n<value_type, size_type, traits_type, \
			npos>(data_, size_, c, pos); \
	} \
	YB_Impl_StringView_search34(_n, _arg)
#define YB_Impl_StringView_search_mf2(_n, _arg, _n2) \
	YB_Impl_StringView_search1(_n, _arg) \
	YB_Impl_StringView_search_fn_head(_n, , ynothrow, _tChar c, \
		size_type pos = _arg) \
		return _n2(c, pos); \
	} \
	YB_Impl_StringView_search34(_n, _arg)

	YB_Impl_StringView_search_mf(find, 0)

	YB_Impl_StringView_search_mf(rfind, npos)

	YB_Impl_StringView_search_mf2(find_first_of, 0, find)

	YB_Impl_StringView_search_mf2(find_last_of, npos, rfind)

	YB_Impl_StringView_search_mf(find_first_not_of, 0)

	YB_Impl_StringView_search_mf(find_last_not_of, npos)

#undef YB_Impl_StringView_search_mf
#undef YB_Impl_StringView_search_mf2
#undef YB_Impl_StringView_search1
#undef YB_Impl_StringView_search34
#undef YB_Impl_StringView_search_fn_head
};

//! \relates basic_string_view
//!@{
template<typename _tChar, class _tTraits>
YB_ATTR_nodiscard YB_PURE yconstfn bool
operator==(basic_string_view<_tChar, _tTraits> x,
	basic_string_view<_tChar, _tTraits> y) ynothrow
{
	return x.compare(y) == 0;
}
template<typename _tChar, class _tTraits>
YB_ATTR_nodiscard YB_PURE yconstfn bool
operator==(basic_string_view<_tChar, _tTraits> x,
	yimpl(decay_t<basic_string_view<_tChar, _tTraits>>) y) ynothrow
{
	return x.compare(y) == 0;
}
//! \since build 642
template<typename _tChar, class _tTraits>
YB_ATTR_nodiscard YB_PURE yconstfn bool
operator==(yimpl(decay_t<basic_string_view<_tChar, _tTraits>>) x,
	basic_string_view<_tChar, _tTraits> y) ynothrow
{
	return x.compare(y) == 0;
}

template<typename _tChar, class _tTraits>
YB_ATTR_nodiscard YB_PURE yconstfn bool
operator<(basic_string_view<_tChar, _tTraits> x,
	basic_string_view<_tChar, _tTraits> y) ynothrow
{
	return x.compare(y) < 0;
}
//! \since build 642
template<typename _tChar, class _tTraits>
YB_ATTR_nodiscard YB_PURE yconstfn bool
operator<(basic_string_view<_tChar, _tTraits> x,
	yimpl(decay_t<basic_string_view<_tChar, _tTraits>>) y) ynothrow
{
	return x.compare(y) < 0;
}
//! \since build 642
template<typename _tChar, class _tTraits>
YB_ATTR_nodiscard YB_PURE yconstfn bool
operator<(yimpl(decay_t<basic_string_view<_tChar, _tTraits>>) x,
	basic_string_view<_tChar, _tTraits> y) ynothrow
{
	return x.compare(y) < 0;
}

template<typename _tChar, class _tTraits>
std::basic_ostream<_tChar, _tTraits>&
operator<<(std::basic_ostream<_tChar, _tTraits>& os,
	basic_string_view<_tChar, _tTraits> str)
{
	// XXX: Better implementation?
	return os << std::basic_string<_tChar, _tTraits>(str.data(), str.size());
}
//!@}
//!@}
#endif

using string_view = basic_string_view<char>;
using u16string_view = basic_string_view<char16_t>;
using u32string_view = basic_string_view<char32_t>;
using wstring_view = basic_string_view<wchar_t>;

} // inline namespace cpp2017;

/*!
\relates basic_string_view
\since build 967
*/
template<typename _tChar, class _tTraits>
struct is_fast_hash<std::hash<basic_string_view<_tChar, _tTraits>>> : false_
{};


/*!
\ingroup YBase_replacement_extensions
\brief 取字符串类类型的值类型对应的字符串视图类型。
\since build 836
*/
template<class _tString>
using string_view_t = basic_string_view<typename _tString::value_type>;

} // namespace ystdex;

#if YB_Has_string_view != 1
namespace std
{

/*!
\ingroup hashers
\brief ystdex::basic_string_view 散列支持。
\see WG21 N4480 5.11[basic_string_view.hash] 。
\since build 640
*/
template<typename _tChar, class _tTraits>
struct hash<ystdex::basic_string_view<_tChar, _tTraits>>
{
	YB_ATTR_nodiscard YB_PURE size_t
	operator()(const ystdex::string_view& k) const yimpl(ynothrow)
	{
		return ystdex::hash_range(k.data(), k.data() + k.size());
	}
};

} // namespace std;
#endif

#endif

